Conversion of lysine to saccharopine by human tissues

Hutzler, Joel; Dancis, Joseph

doi:10.1016/0304-4165(68)90072-x

Cited by 138 publications

(61 citation statements)

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“…We focused mainly on liver and kidney but a number of aspects regarding the function of LOR and SDH in other tissues should be explored hereafter, mainly those concerning their involvement in genetic disorders such as familial hyperlysinaemias. Two types of familial hyperlysinaemia have been described so far : type I is associated with a combined deficiency of the two enzyme activities, LOR and SDH, whereas in familial hyperlysinaemia type II only the dehydrogenase activity is impaired [6,24,25]. A deficiency in the bifunctional LOR\SDH mRNA levels might explain, for example, why there is a combined deficiency in type I disease ; a mutation in only the SDH domain might explain the type II disease.…”

Section: Discussionmentioning

confidence: 99%

“…This pathway has been described in plants [1][2][3][4] and mammals [5][6][7][8][9][10], and its first two reactions are catalysed by enzymic activities known as lysine-oxoglutarate reductase (LOR ; EC 1.5.1.8) and saccharopine dehydrogenase (SDH ; EC 1.5.1.9). The reductase activity condenses lysine and 2-oxoglutarate to form saccharopine [ε-N-(-glutaryl-2)--lysine].…”

Section: Introductionmentioning

confidence: 99%

“…In mammals, the saccharopine pathway is important for lysine catabolism in the liver, and it involves LOR and SDH activities that are biochemically similar to those described in plants [6][7][8][9][10]14]. In baboon and bovine livers these two activities reside on a single polypeptide [14,15] and the bifunctional protein purified from these sources has been named aminoadipic semiAbbreviations used : LOR, lysine-oxoglutarate reductase ; PEG, poly(ethylene glycol) ; SDH, saccharopine dehydrogenase.…”

Section: Introductionmentioning

confidence: 99%

“…Firstly, these enzyme activities are responsible for lysine catabolism in the liver, contributing not only to the general nitrogen balance in the organism but also to the controlled conversion of lysine into ketone bodies [6,7,9,19,20]. Secondly, lysine is an essential amino acid and its supply is therefore required during embryonic development and early childhood.…”

Section: Introductionmentioning

confidence: 99%

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Lysine degradation through the saccharopine pathway in mammals: involvement of both bifunctional and monofunctional lysine-degrading enzymes in mouse

Papes

Kemper

Cord-Neto

et al. 1999

Biochemical Journal

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Lysine-oxoglutarate reductase and saccharopine dehydrogenase are enzymic activities that catalyse the first two steps of lysine degradation through the saccharopine pathway in upper eukaryotes. This paper describes the isolation and characterization of a cDNA clone encoding a bifunctional enzyme bearing domains corresponding to these two enzymic activities. We partly purified those activities from mouse liver and showed for the first time that both a bifunctional lysine-oxoglutarate reductase/saccharopine dehydrogenase and a monofunctional saccharopine dehydrogenase are likely to be present in this organ. Northern analyses indicate the existence of two mRNA species in liver and kidney. The longest molecule, 3.4 kb in size, corresponds to the isolated cDNA and encodes the bifunctional enzyme. The 2.4 kb short transcript probably codes for the monofunctional dehydrogenase. Sequence analyses show that the bifunctional enzyme is likely to be a mitochondrial protein. Furthermore, enzymic and expression analyses suggest that lysine-oxoglutarate reductase/saccharopine dehydrogenase levels increase in livers of mice under starvation. Lysine-injected mice also show an increase in lysine-oxoglutarate reductase and saccharopine dehydrogenase levels.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Lysine degradation through the saccharopine pathway in mammals: involvement of both bifunctional and monofunctional lysine-degrading enzymes in mouse

Papes

Kemper

Cord-Neto

et al. 1999

Biochemical Journal

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“…The assay mixture contained K-phosphate (pH 7.0; 300 ,umol), L-lysine (50 ,pmol), a-ketoglutarate (25 ,umol), NADPH (300 nmol), and enzyme (0.1-0.2 mg protein) in a total volume of 3 ml. The mixture was incubated at 30°C, and oxidation of NADPH was monitored in a spectrophotometer at 340 nm.Lysine-ketoglutarate reductase catalyzes the following reaction: lysine + a-ketoglutarate + NADPH -* saccharopine + NADP+ The enzyme has been characterized in human and animal tissues (3,7,8) where it is believed to catalyze the first step of lysine catabolism (4). A similar reaction involving NAD is catalyzed by saccharopine dehydrogenase, an enzyme found in yeast and fungi where the reverse of the above reaction is considered to be the final step of lysine biosynthesis (5,6,12,16).…”

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Lysine-Ketoglutarate Reductase Activity in Developing Maize Endosperm

Arruda¹,

Sodek²,

Silva³

1982

Plant Physiol.

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Lysine-ketoglutarate reductase activity was detected and characterzed in the developing endosperm of maize (Zea mays L). The enzyme showed specificity for its substrates: lysine, a-ketoglutarate, and NADPH. Formation of the reaction product saccharopine was demonstrated. The pH optimum of the enzyme was cdose to 7, and the Km for lysine and aketoglutarate were 5.2 and 1.8 millmolar, respectively. between 25 and 70%o saturation was collected and taken up in 2.5 ml of extraction buffer. After desalting on a Sephadex G-25 column (1.5 x 16 cm), the protein fraction was assayed for lysineketoglutarate reductase activity using conditions based on those described by Hutzler and Dancis (7). The assay mixture contained K-phosphate (pH 7.0; 300 ,umol), L-lysine (50 ,pmol), a-ketoglutarate (25 ,umol), NADPH (300 nmol), and enzyme (0.1-0.2 mg protein) in a total volume of 3 ml. The mixture was incubated at 30°C, and oxidation of NADPH was monitored in a spectrophotometer at 340 nm.Lysine-ketoglutarate reductase catalyzes the following reaction: lysine + a-ketoglutarate + NADPH -* saccharopine + NADP+ The enzyme has been characterized in human and animal tissues (3,7,8) where it is believed to catalyze the first step of lysine catabolism (4). A similar reaction involving NAD is catalyzed by saccharopine dehydrogenase, an enzyme found in yeast and fungi where the reverse of the above reaction is considered to be the final step of lysine biosynthesis (5,6,12,16). Thus, in some organisms saccharopine is an intermediate of lysine biosynthesis while in the others it appears to be involved in lysine breakdown. Actually, several pathways for lysine catabolism are known (11), but in higher plants no general pathway has been established. Nevertheless, tracer studies with barley seedlings have provided strong evidence for the pathway involving saccharopine as intermediate (10), suggesting that this route may be important for lysine breakdown in cereals at least. However, we are unaware of any studies with enzymes in higher plants in support of this pathway.In this report, we describe the characterization of lysine-ketoglutarate reductase in developing maize endosperm, a tissue known to degrade lysine extensively (14). MATERIALS AND METHODS RESULTS AND DISCUSSIONThe data in Table I show that partially purified extracts of maize endosperm oxidized NADPH in the presence of lysine and a-ketoglutarate. In the absence of one or both of these substrates, the oxidation of NADPH was minimal. Specificity for the substrates is indicated by the fact that several amino acids, including closely related structures such as L-ornithine and D-lysine, would not substitute for L-lysine, nor would oxaloacetate or pyruvate substitute for a-ketoglutarate. NADH would not replace NADPH as electron donor, as was found for the enzyme from human liver (7).To confirm that the activity being measured was truly lysineketoglutarate reductase, it would be essential to demonstrate the formation of saccharopine in the assay. This was attempted using I4CJlysine...

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